SkIndia Quiz 37: A Persistent Plaque in the Pubic Region.

A 70-year-old man presented with an itchy eczematous well-defined plaque of size 10 × 7 cm involving the pubic region, penis, and scrotum. It was eroded at places and covered with grayish-white scales and crusts [Figure 1]. The lesion had persisted almost unchanged for 15 years despite treatment. Skin biopsy stained with hematoxylin and eosin stain showed characteristic features [Figure 2a and b]. Special stain with mucicarmine was positive [Figure 3]. Immunohistochemistry markers were positive for CK7 and negative for CK20 and CEA [Figure 4]. Whole body positron emission tomography scan did not reveal any abnormality.

Figure 1

An erythematous, eczematous plaque over pubic region, penis, and scrotum

Figure 2

(a and b) Histology showing large cells with abundant pale-staining cytoplasm and pleomorphic nuclei in the epidermis. (H and E, ×40 and ×100)

Figure 3

Characteristic cells showing mucicarmine stain positivity (×20)

Figure 4

Immunohistochemistry showing positive staining with CK7 (×40)

Question

What is your diagnosis?

Histology showed circumscribed collections of large cells with abundant pale-staining cytoplasm and pleomorphic nuclei in the epidermis [Figure 2]. Some of the cells had a “signet ring” appearance. Staining with mucicarmine was positive [Figure 3]. On immunohistochemistry [Figure 4], these cells were positive for cytokeratin 7(CK7) but negative for cytokeratin 20(CK20) and carcinoembryonic antigen (CEA).

Answer

Extramammary Paget's disease.

Discussion

Extramammary Paget's disease (EMPD) is a rare neoplasm of the apocrine gland bearing skin that presents as a slowly spreading, erythematous or leukoplakic, marginated plaque. The lesion can be eczematous, crusted, scaly, or occasionally ulcerated.[1] The hallmark of EMPD is its relentless progression despite topical therapy.

EMPD encompasses two different forms: Primary and secondary. The primary EMPD is initially limited to the epithelium and is not associated with distant adenocarcinoma. The secondary form is associated with an underlying adenocarcinoma from dermal adnexal glands or contiguous epithelium, usually of genitourinary or gastrointestinal tract.[2]

Diagnosis of EMPD rests on histological identification of Paget's cells that show strong cytoplasmic staining for Periodic acid-Schiff (PAS), mucicarmine and alcian blue. They also react positively with anti-cytokeratin (CAM 5.2), epithelial membrane antigen (EMA), cytokeratin 7 (CK7), CEA, and gross cystic disease fluid protein-15 (GCDFP-15).[3]

Wide surgical excision or Moh's micrographic surgery is the treatment of choice for EMPD. Topical treatment with imiquimod, bleomycin or 5-flurouracil, photodynamic therapy, radiotherapy, and laser therapy have been tried.[4] There is a need for long-term follow-up to exclude recurrence of disease or development of an associated malignancy.

Learning points

Any long-standing eczematous plaque in the apocrine gland–bearing areas that defies conventional treatment should arouse the suspicion of EMPD

Early recognition followed by biopsy and histological confirmation are crucial for timely surgical intervention

The patient should be investigated for underlying malignancies of the gastrointestinal and genitourinary tract

Histology is quite characteristic and shows cells with abundant pale-staining cytoplasm and pleomorphic nuclei (signet ring cells).

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.