Solitary late spinal metastasis from apocrine salivary duct carcinoma: Case report.

BACKGROUND: The salivary duct carcinomas (SDCs) are rare, high-grade neoplasms involving major salivary glands. Parotid is the most frequently involved gland (85%). Apocrine phenotype (histological presence of decapitation secretions) and androgen reception expression define SDC. The clinical course of these tumors is characterized by aggressive local behavior with extraglandular extension, high recurrence rates, early metastases, and poor prognoses. Despite aggressive surgical/radiation therapy management, the rates of locoregional and metastatic relapses are high, and the mortality rates over 48 months approach 65%. Notably, there is no treatment algorithm available for managing vertebral metastases from apocrine SDC. CASE DESCRIPTION: An elderly male presented with MR/CT findings of an isolated T11 vertebral metastasis attributed to a previously treated parotid SDC. On both CT/MR, it was an osteolytic lesion and demonstrated spinal canal infiltration. The patient underwent surgical biopsy/decompression/resection, following which the lesion histopathologically proved to be a SDC. The patient was subsequently treated with 30 Gy in 10 fractions within 2 weeks of discharge. One-month later, the MRI confirmed adequate epidural decompression without recurrence, and 9 months post-operatively, patient remained disease free.
CONCLUSION: Isolated metastasis attributed to parotid SDC followed by radiation therapy may result in tumor control. Copyright:

INTRODUCTION

Salivary duct carcinomas (SDCs) are rare and account for approximately 6% of all malignant salivary gland tumors. SDC are malignant, rapidly-growing aggressive tumors with a high local recurrence rate, and high frequency of early metastases.[7,10,14,16,18] In this report, we present a 77-year-old man male with an isolated T11 vertebral metastasis from a primary apocrine SDC of the parotid gland who was adequately managed with biopsy/surgical resection followed by radiation therapy.

CASE REPORT

Initial presentation of SDC

A 77-year-old male with a medical history of the left-sided parotid carcinoma presented with the MR/CT finding of an isolated metastatic T11 vertebral lesion diagnosed following a radical parotidectomy. The histological diagnosis was consistent with a SDC with apocrine differentiation. At that time, 3 lymph nodes were positive, and the patient, therefore, underwent subsequently adjuvant local radiotherapy.

Presentation with T11 metastatic SDC disease

A chest-abdomen CT scan, performed 3 months later, showed an increase in size of the vertebral lesion and highlighted spinal instability. Further, the spinal MRI demonstrated infiltration of the spinal canal at the T11 level due to the SDC (i.e., Bilsky Grade 2 epidural compression) [Figures 1a and b].[2] The patient underwent biopsy/surgical decompression/resection of the tumor utilizing a left T11 laminectomy. At surgery, the left T11 pedicle was removed, followed by partial T11 corpectomy and the posterior application of two carbon rods from T10 to T12 [Figure 2a]. The postoperative spinal CT scan confirmed that the fixation system was accurately placed and that the spinal cord was sufficiently decompressed [Figures 2b and c].

Figure 1:

Sagittal (a) and axial (b) preoperative MRI showing epidural compression and circumferential vertebral involvement.

Figure 2:

Intraoperative image (a) displaying the circumferential decompression and vertebral fixation with carbon fiber system. Postoperative sagittal (b) and axial (c) CT scan showing the accuracy of fixation system placement. Postoperative MRI image (d) demonstrating the epidural decompression and the absence of local disease recurrence.

Histology

The initial histological diagnosis was consistent with a SDC with apocrine differentiation and 3 lymph nodes were positive. The T11 histopathology was the same. Immunohistochemical stainings for gross cystic disease fluid protein-15 (GCDFP15) and androgen receptor (e.g., for the T11 biopsy material) were diffusely positive; while cytokeratins 8/18 were focally positive [Figures 3a, b, c, d and e], all remaining consistent with the diagnosis of a SDC.

Figure 3:

Histological findings after vertebral lesion resection. H and E image (a: 100X, b: 200X) shows a bone infiltrating metastatic carcinoma with duct structures and comedonecrosis. Neoplastic cells were mildly pleomorphic with an eosinophilic cytoplasm and features consistent with apocrine differentiation. Immunohistochemical stainings showed a diffuse positivity for GCDFP15 (c) and androgen receptor (d), while cytokeratins 8/18 were focally positive (e).

Adjuvant radiation therapy

Subsequently, patient underwent adjuvant local radiotherapy and received 30 Gy in 10 fractions within 2 postoperative weeks. One-month post-operatively, the MRI confirmed adequate epidural decompression without tumor recurrence [Figure 2d]. Nine months later, the patient remained disease free [Table 1].

Table 1:

Case report details.

DISCUSSION

SDC are rare, high-grade neoplasms involving major salivary glands, and represent approximately 6% of all salivary gland cancers.[12,15] The parotid gland is the most frequent involved (75–85%). The peak of incidence occurs in the 6th–7th decades of life, and there is a male predominance. Patients present with enlarging parotid masses, frequently associated with VII cranial nerve dysfunction, plus aggressive local behavior (i.e., with extraglandular extension), high recurrence rates, and early metastases correlating with poor prognoses.[10,14,16,18]

Prognosis with surgery and radiation therapy

Although there is no specific management algorithm for the treatment of vertebral metastases from SDCs, those with single osteolytic lesions and high-grade epidural compression may be successfully treated with aggressive gross-total surgical resection followed by radiation therapy.[1,3-6,8,9,13] Due to the frequency of SCD’s invasion and their aggressive nature, surgical treatment should include a radical/ total parotidectomy with sacrifice of the facial nerve and ipsilateral lymph node dissection, followed by postoperative chemotherapy/radiotherapy. Even with such aggressive management, there is a nearly 65% locoregional rate of metastatic relapse, and patients typically succumb from recurrent and/or progressive disease within 48 months.[10]

Apocrine phenotype (histological presence of decapitation secretions) and androgen receptor expression defines SDC that may metastasize to the spine (e.g., to the T11 level in this case) warranting surgical extirpation followed by adjuvant radiation therapy.[11,17]

CONCLUSION

Three-year delayed metastatic parotid carcinoma of the T11 vertebral body was adequately managed with separation surgery achieved through an extracavitary transpedicular partial anterior corpectomy and posterior pedicle screw fusion, followed by radiation therapy.