Track: Clinical Studies

Topic: Neoplasia,Carcinogensis,Tumor Biology

Abstract:

Hidradenocarcinoma (HAC) is a rare cutaneous adnexal tumor that arises de novo or in association with a hidradenoma (HA). HACs often present as solitary, slow-growing tumors that can recur locally and have regional and distant metastasis. Classifying adnexal tumors histologically can present a diagnostic dilemma due to overlapping morphologic features.

Our retrospective study includes 16 patients (6 females, 10 males), ranging from 43 to 79 years (median 54.5). Tumor size ranged from 1.5 to 8.6 cm, and were located on the trunk (2), scalp (4), and extremities (10). Five cases were associated with preexisting HA. Thirteen tumors showed low-grade (LGr) cytology and three demonstrated high-grade (HGr) cytology. Lymphovascular invasion (LVI) was present in 4 cases and necrosis in 8 cases.

All tumors expressed p40, retained YAP-N and YAP-C, and were negative for NUT and PRAME. Tumor cells were positive for EMA (15/16), CEA (7/16), and c-kit (12/16). Available follow-up ranged from 3-146 months (median 44). LVI and HGr cytology were associated with decreased disease-specific survival when compared to cases without LVI and LGr cytology (DSS, median 35 vs. 51 months, p<0.001). Three cases developed metastases (within 4-35 months), of which two demonstrated CRTC1::MAML2 and EML4::ALK fusions, respectively. The third case had PIK3CA, TP53 alterations, and SMARCA4 missense mutation.

In conclusion, HAC remains a histomorphological diagnosis with limited data for risk stratification and treatments. Early molecular tumor profiling in cases with HGr cytology and LVI may aid in prognosis. The role of molecular ancillary testing in HAC remains to be determined.

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Geetha Jagannathan, MD