MAML2 Positive Nodular Hidradenoma Presenting as a Subcutaneous Submental Mass – The Importance of Clinical Correlation

Introduction

Nodular hidradenomas are benign adnexal neoplasms presenting as solitary asymptomatic intradermal nodules, often on facial skin. Tumors are covered by normal skin, but superficial ulcers may occur. Hidradenomas often exhibit cuboidal cells with pink cytoplasm, but clear cell, squamoid, plasmacytoid, and mucinous variants have been described. Malignant counterpart of hidradenoma exists. There is morphologic and molecular overlap between cutaneous adnexal tumors and salivary gland tumors, for example, hidradenoma and mucoepidermoid carcinoma (MEC).

Case Findings

A 64-year-old male patient presented with a submental subcutaneous mass for six months. A fine needle aspiration (FNA) was performed, based on the clinical suspicion for a granulomatous process and to rule out malignancy. FNA cytology was interpreted as positive for malignant cells, suspicious for squamous cell carcinoma (SCC). Constituent cells were p40 positive and negative for p16, androgen receptor (AR), and CD163. AFB staining negative for acid fast bacilli. Excision of the lesion was performed.

Results

Microscopic examination reveals a fragmented epithelioid tumor with squamoid, clear cell, glandular, and papillary features favoring a benign adnexal skin tumor. The proliferative index was < 5%. Included in the differential diagnosis was MEC. Positive MAML2 gene rearrangement was identified on fluorescent in-situ hybridization (FISH). Upon consultation with dermatopathology, a diagnosis of benign nodular hidradenoma was rendered.

Conclusions

Clinical presentation, discussed with the surgeon, excluded association with salivary glands, emphasizing the subcutaneous location. Although there is morphologic and molecular overlap between nodular hidradenoma and MEC, clinical location supports the final diagnosis of a benign adnexal tumor, specifically benign nodular hidradenoma. In addition, MAML2 interrogation can help distinguish hidradenoma from other sweat gland neoplasms.