Immunoglobulin G4-Related Disease of the Ovary Mimicking Bilateral Ovarian Malignancies.

Immunoglobulin G4-related disease (IgG4-RD) is a fibro-inflammatory condition characterized by several pathological features that can theoretically involve all organs. Ovarian involvement in IgG4-RD has been reported by two studies only. Herein, we report a pathologically confirmed case of ovarian involvement of IgG4-RD, which mimicked bilateral ovarian malignancies on computed tomography and magnetic resonance imaging. Copyrights

INTRODUCTION

Immunoglobulin G4-related disease (IgG4-RD) is a recently recognized fibro-inflammatory condition that is characterized by several pathological features (1). Although elevated serum IgG4 concentration has been reported to be associated with IgG4-RD and to have modestly high sensitivity and specificity (234), pathologic tissue confirmation remains the ultimate gold standard for diagnosing IgG4-RD. IgG4-RD has been reported in various organs including pancreas, liver, bile duct, lung, pleura, kidney, aorta, lymph node, lacrimal gland, salivary gland, skin, paranasal sinus (5). Within the scope of our investigation, however, only two recent publications have described ovarian involvement of IgG4-RD (67). Herein, we report a case of rare ovarian involvement of IgG4-RD with literature review.

CASE REPORT

A 53-year-old woman presented to the gynecology department for one month of persistent abdominal pain. She had no significant medical history other than dyslipidemia. An initial abdominopelvic computed tomography (CT) scan revealed solid, oval-shaped, poorly enhancing mass-like enlargement of bilateral ovaries (Fig. 1A). The left ovary measured 6.3 cm × 4.1 cm and the right one measured 5.4 cm × 3.7 cm. Multiple conglomerated precaval and paraaortic lymph nodes measuring up to 2.4 cm in the longest diameter were also noted (Fig. 1A). T2-weighted magnetic resonance (MR) images showed high signal intensity of internal stroma and relatively low signal intensity of the peripheral portion of both ovaries, while T1-weighted images showed homogeneously isointense to slightly hyperintense signal intensity of the ovaries compared to that of the myometrium (Fig. 1B). Gadolinium contrast-enhanced T1-weighted images demonstrated subtle enhancement in the peripheral portion of the ovaries where the T2 signal intensity was relatively low (Fig. 1B). Based on the CT and MRI, our differential diagnosis included bilateral ovarian metastases (Krukenberg tumor) and sex-cord stromal tumors such as granulosa cell tumor. Positron emission tomography-CT (PET-CT) demonstrated mild 18F-fluorodeoxyglucose (FDG) uptake in bilateral ovaries [standardized uptake values (SUV): 2.5 and 2.4, left and right, respectively] and intense 18F-FDG uptake in the left paraaortic lymph node (SUV: 4.14) (Fig. 1C). None of serum tumor markers was reported to be elevated; cancer antigen (CA)-125 17.6 (U/mL), human epididymis protein 4 40.9 (pmol/L), carcinoembryonic antigen 1.19 (ng/mL), CA 19-9 21.6 (U/mL) and alpha-fetoprotein < 0.5 (ng/mL). The serum IgG4 level was not measured.

Fig. 1

A 53-year-old woman diagnosed with IgG4-related disease involving both ovaries.

A. Axial contrast-enhanced CT images demonstrate oval-shaped, poorly enhancing solid mass-like enlargement of both ovaries (left, arrowheads). The left ovary measures 6.3 cm × 4.1 cm and the right one measures 5.4 cm × 3.7 cm. The average post-contrast attenuation numbers of left and right ovaries are 34.9 HU and 37.7 HU respectively, which were 22.7 HU and 23.9 HU on pre-contrast CT scans (not shown). Several enlarged and conglomerated lymph nodes are noted in paraaortic and aortocaval space (right). The largest node, situated at the level of mid kidney measures 2.4 cm in the longest diameter (arrow). Contrast enhancement of the enlarged lymph nodes appears homogeneous and there is no evidence of internal necrosis.

B. T1WI (left) shows homogeneously isointense to slightly hyperintense signal intensity of the right ovary compared to that of the myometrium (arrow). T2WI (middle) shows high signal intensity of the internal stroma of the ovary and relatively low signal intensity of the peripheral portion (arrow). Gadolinium CET1 (right) shows subtle enhancement in the peripheral portion of the right ovary, where the T2 signal intensity is relatively low (arrow). The left ovary is not included in the same plane.

C. PET-CT scans demonstrate mild 18F-FDG uptake in both ovaries (SUVs were 2.5 and 2.4 for the left (thick arrow) and right ovaries (arrowhead), respectively). An enlarged left paraaortic lymph node shows intense 18F-FDG uptake (SUV: 4.14) (arrows). No other abnormal 18F-FDG uptake is observed in the scanned abdomen and pelvis.

D. Bilaterally enlarged ovaries (approximately 5 cm × 5 cm) are observed during exploratory laparoscopy.

E. H&E stained sections of ovarian tissue (left: × 12.5, middle: × 100, right: × 400) demonstrate lymphoid follicular hyperplasia (arrows) with dense plasmacytic infiltration (plasma cells are indicated by arrowheads) with a few eosinophils (thick arrows).

F. Immunohistochemistry with anti- IgG and IgG4 monoclonal antibodies reveals IgG-positive (240/HPF) (left) and IgG4-positive plasma cells (120/HPF) (right).

CET1 = contrast-enhanced T1WI, FDG = fluorodeoxyglucose, HU = Hounsfield unit, IgG4 = Immunoglobulin G4, SUV = standardized uptake value, T1WI = T1-weighted image, T2WI = T2-weighted image, IgG = Immunoglobulin G, H&E = hematoxylin and eosin, HPF = high-power field

She underwent an elective exploratory laparoscopy. About 5 cm × 5 cm sized left, and right ovarian masses were noted (Fig. 1D) in the pelvic cavity. The excised ovaries weighed 39 g and 30 g, left and right, respectively. Bilateral salpingo-oophorectomy was performed. Benign stromal tumors were reported in the frozen section of both ovaries. The final pathologic evaluation reported lymphoid follicular hyperplasia with dense plasmacytic infiltration involving bilateral ovaries and paratubal tissue. (Fig. 1E). Additional immunohistochemistry using monoclonal antibodies against IgG and IgG4 was performed (Fig. 1F). The estimated IgG-positive plasma cell count was 240 per high-power field (HPF), IgG4-positive plasma cell count was 120/HPF and the calculated IgG4-positive to IgG-positive plasma cell ratio was 50%. Unlike other organs, the cutoff value of IgG-positive plasma cell count for the diagnosis of ovarian IgG4-RD has not been proposed yet. Nonetheless, the pathology result of the patient fulfilled at least one of three major pathological features and mandatory IgG4-positive to IgG-positive plasma cell ratio of 40%. In addition, the number of IgG4-positive cells per HPF exceeded the reference values of most organs (10, 30, 50 or 100/HPF) except for the reference value proposed for skin (200/HPF). Through the multidisciplinary discussion of gynecologists, radiologists and pathologists, other possible diagnoses were excluded and the collaborated diagnosis of IgG4-RD was adopted. Within a few days, the patient was discharged without complication. At the first follow-up two months later, the patient had no symptom and ultrasonography was unremarkable. The clinician decided not to add any treatment and planned another follow-up schedule a year later.

DISCUSSION

IgG4-RD a fibro-inflammatory condition that is characterized by several pathological features and theoretically capable of involving any organ. According to the consensus statement on the pathology of IgG4-RD by Deshpande et al. (1), the diagnosis of IgG4-RD requires collaborated pathological and clinical investigations. To establish a histopathological diagnosis of IgG4-RD, not only at least one of three major histopathological features; 1) dense lymphoplasmacytic infiltrates, 2) fibrosis arranged at least focally in a storiform pattern, 3) obliterative phlebitis, but increased IgG4-positive plasma cell count (or an increased ratio of IgG-positive cell to IgG4-positive cell count) in biopsied or excised tissue should be fulfilled (5). If any two of the three major criteria are met and the number of IgG4 positive cells exceeds the cutoff value with an IgG4(+)/IgG(+) ratio over 40%, the top-tiered diagnosis of “Histologically highly suggestive of IgG4-RD” can be suggested. The proposed cutoff values differ by organs, ranging from 10/HPF (meninges and liver) to 200/HPF (skin). Also, the lacrimal gland requires only one major criterion as an exception. The second tier diagnosis called “probable histological features of IgG4-RD” consists of cases presented by a single criterion, cases of inconclusive pathology obtained by needle biopsy and cases involving organs with limited published data (i.e. meningeal and cutaneous disease). To confirm the diagnosis of these “probable” cases of IgG4-RD, additional clinical, radiological or serological findings such as elevated serum IgG4 level above 135 mg/dL or involvement of other organs should be demonstrated.

In order to recognize the ovary as a new involvement site of IgG4-related disease, it is necessary to meet stricter criteria according to the consensus statement; 1) characteristic histopathological findings with an elevated IgG4-positive plasma cells and IgG4-to-IgG ratio, 2) high serum IgG4 concentrations, 3) effective response to glucocorticoid therapy, 4) other organ involvement that is consistent with IgG4-related disease. Maruyama et al. (6) recently reported a case of IgG4-RD involving bilateral ovaries which met all of three typical histopathologic features, while Sekulic et al. (7) reported a case of IgG4-RD involving left ovary which met two of the three major histopathologic features (dense lymphoplasmacytic infiltrates and obliterative phlebitis) of the IgG4-RD (Table 1). In the case of Maruyama et al. (6), serum IgG4 level was above 1000 mg/dL to meet the second criterion. On the other hand, serum IgG4 levels were not reported in the case of Sekulic et al. (7) and in our case. However, Maruyama et al. (6) somehow reported the number of infiltrating lymphoplasmacytic cells (300/HPF) instead of estimating IgG-positive cells, which made their case insufficient to meet the required criteria. Other organ involvement as the fourth criterion was assumed in Maruyama's case (mesenteric nodules and lymph nodes) and in our case (paraaortic lymph nodes). Above all, none of the reported cases was initiated with glucocorticoid therapy and the response to glucocorticoid has never been evaluated. Thus far, there are limited evidence to declare the ovary as a new involvement site of IgG4-RD. However, the spectrum of IgG4-RD has been expanding and the ovary is likely to be considered a new involvement site in the near future. Radiologically, the case of Maruyama et al. (6) showed a 14 cm multinodular pelvic mass with mesenteric nodules on MRI mimicking ovarian malignancy, while the case of Sekulic et al. (7) revealed normal-sized ovaries. Our case has shown bilateral ovarian enlargement with paraaortic lymphadenopathy.

Table 1

Characteristics of Reported Cases of IgG4-Related Disease Involving the Ovary

References	Patient Age	Radiologic Features	Major Histopathologic Features	IgG4+Count, IgG+/IgG4+Ratio	Serum IgG4 Level	Response to Glucocorticoid	Other Organ Involvement
Maruyama et al. (6) (2016)	59	Multinodular solid mass (14 cm)	3/3 (lymphoplasmacytic infiltration, storiform fibrosis, and obliterative phlebitis)	Does not meet criteria	1000 mg/dL	Not tried	Mesenteric nodules, lymph nodes
		• T1WI: homogeneously low SI
		• T2WI: heterogeneous SI
		• CE−T1WI: diffuse contrast enhancement
Sekulic et al. (7) (2017)	47	Normal sized ovaries	2/3 (lymphoplasmacytic infiltration and obliterative phlebitis)	40–50/HPF, 40–50%	Not measured	Not tried	None
Current case	53	Enlarged bilateral ovaries (6.5 cm, 5.1 cm)	1/3 (lymphoplasmacytic infiltration)	120/HPF, 50%	Not measured	Not tried	Paraaortic lymph nodes
		• T1WI: homogeneously isointense
		• T2WI: heterogeneous SI
		• CE-T1WI: subtle peripheral contrast enhancement

CE = contrast enhanced, HPF = high-power field, IgG4 = Immunoglobulin G4, SI = signal intensity, T1WI = T1-weighted image, T2WI = T2-weighted image

In conclusion, we reported a rare case of IgG4-RD involving bilateral ovaries diagnosed by an interdisciplinary approach. In our opinion, the ovary needs to be investigated as a new site of IgG4-RD involvement, despite limited documentation. The acceptable cutoff value of IgG4-positive plasma cell count for the ovary should also be carefully estimated. Radiologically, IgG4-RD of the ovary may mimic bilateral ovarian malignancy on CT and MRI due to its solid nature and potential for associated lymphadenopathy.