Clear Cell Hidradenoma of the Breast Diagnosed on a Core Needle Biopsy: A case report and review of the literature

Clear cell hidradenoma of the male breast: A case report and literature review

INTRODUCTION

Clear cell hidradenoma (CCH) is a rare type of benign breast tumor that may undergo malignant transformation in a few cases. It clinically manifests as a painless breast mass, and may include nipple discharge. Complete surgical excision with adequate safety margins is the primary treatment.

PRESENTATION OF CASE

A 34-year-old man developed a mass beneath the left nipple over 2 years. Although the mass was painless, it gradually enlarged over time and was accompanied by nipple discharge. Complete excision of the mass revealed that the tumor cells were arranged in solid nodule-like structures composed of clear cells and few cells with eosinophilic cytoplasm. Based on the results of immunohistochemical staining and MAML2 rearrangement analysis, a pathological diagnosis of breast CCH was made. The patient was followed up postoperatively for six months, during which there was no recurrence.

DISCUSSION

Breast CCH differentiates from low-grade mucoepidermoid, glycogen-rich, and lipid-rich breast carcinomas. A more comprehensive understanding of breast CCH can aid pathologists in avoiding misdiagnoses during fine-needle aspiration biopsy and intraoperative frozen section diagnosis. Diagnostic clues for CCH include: (1) the presence of two types of cell morphology in the tumor, (2) immunohistochemical staining indicating p63 positivity, (3) negativity for myoepithelial markers, and (4) MAML2 gene rearrangement in certain cases.

CONCLUSION

The case we reported occurred in a male patient with MAML2 gene rearrangement, which is extremely rare. Complete surgical excision with adequate safety margins is the primary treatment method for breast CCH, and close postoperative follow-up should be conducted to monitor disease recurrence.

Challenging diagnosis of male intraductal papilloma masquerading as eccrine hidradenoma in the breast: Case report

RATIONALE

This article presents a challenging case involving an elderly male patient with a misdiagnosed intraductal mammary papilloma initially identified as a sweat adenoma through ultrasound imaging. The study aims to explore the histopathology, clinical presentations, and sonographic features of both conditions, emphasizing the contributing factors to the diagnostic misstep.

PATIENT CONCERNS

A 61-year-old male reported a persistent left breast mass, along with pain and swelling, spanning a 6-month duration.

DIAGNOSES

Ultrasound examination indicated a deep, square, mixed-echo mass in the left nipple, initially suggestive of a sweat adenoma. However, subsequent pathological analysis following resection under general anesthesia confirmed an intraductal papilloma.

INTERVENTION

The patient underwent surgical resection of the left breast mass under general anesthesia.

OUTCOME

Post-surgery, the patient exhibited satisfactory recovery; however, regrettably, he was lost to follow-up.

LESSONS

This study underscores the challenge in differentiating between clear cell sweat adenoma and male intraductal mammary papilloma solely based on ultrasonic characteristics. It emphasizes the susceptibility of ultrasound-based diagnoses to misinterpretation, highlighting the critical need for a comprehensive pathological examination to establish a definitive diagnosis.

Genetic and Immunohistochemical Profiling of Mammary Hidradenoma and Comparison to Mucoepidermoid Carcinoma

Mucoepidermoid carcinoma (MEC) is exceedingly rare in the breast, with <45 cases reported in the literature. Although estrogen receptor/progesterone receptor/human epidermal growth factor 2 triple-negative, MEC is characterized as a special subtype of breast carcinoma with significantly better prognosis than conventional basal-type tumors. Cutaneous hidradenoma (HA) is considered a benign adnexal neoplasm showing histomorphologic overlap with MEC. Rare cases of HA have also been reported in the breast, but these are relatively uncharacterized. In this study, we examined the clinicopathologic, immunohistochemical (IHC), and genetic features of 8 breast HAs, in comparison to 3 mammary MECs. All cases were positive for MAML2 break-apart fluorescence in situ hybridization. Eight cases demonstrated a CRTC1::MAML2 fusion, and one MEC harbored a CRTC3::MAML2 fusion; the latter is a novel finding in the breast. Mutational burden was very low, with only one HA exhibiting a MAP3K1 pathogenic alteration. By IHC, both MEC and HA demonstrated cell type-dependent expression of high- and low-molecular-weight keratins and p63, as well as negative to low-positive estrogen receptor and androgen receptor. Smooth muscle myosin and calponin highlighted an in situ component in the 3 cases of MEC; expression of these myoepithelial markers was negative in HAs. Additional distinguishing characteristics included the growth pattern and tumor architecture, the presence of glandular/luminal cells in HA, and overall higher IHC expression of SOX10, S100 protein, MUC4, and mammaglobin in MEC. Morphologic findings were also compared to a series of 27 cutaneous nonmammary HAs. Mucinous and glandular/luminal cells were identified in significantly more mammary HAs than nonmammary lesions. The findings provide insight into the pathogenesis of MAML2-rearranged neoplasms of the breast, underscore the overlapping genetic features of MEC and HA, and highlight similarities to their extramammary counterparts.