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Indian J Dermatol
Indian J Dermatol
IJD
Indian J Dermatol
Indian Journal of Dermatology
0019-5154
1998-3611
Wolters Kluwer - Medknow India

IJD-69-348
10.4103/ijd.ijd_71_24
Correspondences
Isolated Tubular Apocrine Adenoma of Axilla: Atypical Microscopic Manifestations in an Uncommon Entity
Palo Seetu
Somalwar Shrinivas Bheemrao
Ramavath Krishna 1
From the Department of Pathology and Laboratory Medicine, All India Institute of Medical Sciences, Bibinagar, Telangana, Hyderabad, India E-mail: seetu.pearl@gmail.com
1 Department of General Surgery, All India Institute of Medical Sciences, Bibinagar, Telangana, Hyderabad, India
Jul-Aug 2024
19 8 2024
69 4 348350
1 2024
3 2024
Copyright: © 2024 Indian Journal of Dermatology
2024
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pmcDear Editor,

Tubular apocrine adenoma (TAA) is an uncommon benign adnexal neoplasm which typically presents as a dermal-based neoplasm and is commonly encountered on the scalp, often in association with syringocystadenoma papilliferum.[123] Here, we describe an unusual case of an isolated TAA arising in the axilla and discuss its peculiar microscopic features.

A 32-year-old female presented with a swelling, associated with intermittent pain, in the left axillary region for 3 years. On local examination, it was a firm, polypoidal, cutaneous growth of 2 × 1.5 × 1 cm. Axillary lymph nodes were not palpable. With a provisional clinical diagnosis of squamous papilloma, an excisional biopsy was performed. Microscopy revealed a fairly circumscribed dermal-based neoplasm with an epidermal connection. The tumour was composed of variably sized tubules lined by double to multi-layer cuboidal cells, displaying round to oval nuclei, conspicuous nucleoli and eosinophilic cytoplasm. Few tubules were cystically dilated and filled with granular eosinophilic material and few exhibited intraluminal psuedopapillae. A focal area of closely packed tubules with scant intervening stroma and frequent mitotic activity was noted. However, there was no evidence of marked pleomorphism or invasive growth pattern. Intervening and peritumoral stroma showed a desmoplastic and dense lymphoplasmacytic response, with germinal centre formation [Figure 1a-e]. A final diagnosis of tubular apocrine adenoma was rendered. The postoperative course was uneventful.

Figure 1 (a) Microphotograph showing dermal-based tumour with epidermal connection and comprising variably-sized tubules (40×, hematoxylin and eosin); (b) Peritumoral area showing intense lymphoplasmacytic response (red arrow) (40×, hematoxylin and eosin); (c) High power showing glands lined by dual to multi-layered epithelium. A mitotic figure is circled (400×, hematoxylin and eosin); (d) A focus (left) showing closely packed tubules with scant intervening stroma (100×, hematoxylin and eosin); (e) High power showing closely packed tubules with mitotic figures (circled) (40×, hematoxylin and eosin); (f) Immunohistochemistry for smooth muscle actin exhibiting continuous positivity around the tubules

Documented cases of pure TAA, like in our case, are scarce. Moreover, in our case, pure TAA showed an epidermal connection, which is also very rare.[12] The tumour elicited an intense immune response in the form of dense lymphocytic infiltrate at the peri-tumoural area, another rare feature. Notably, the tumour exhibited certain alarming features such as increased mitotic activity and back-to-back arrangement of the tubulo-glandular structures. This was a very peculiar microscopic finding and has not been documented in TAA to date. In such cases, ruling out co-existing malignancy, especially apocrine carcinoma, is imperative. Bujas et al.[4] reported a case of axillary apocrine carcinoma associated with apocrine adenoma in a 79-year-old woman. Microscopically, it was a poorly demarcated neoplasm located in the dermis, and apart from areas of closely packed tubulo-glandular structures, it was also associated with epidermal ulceration, focal necrosis, nuclear pleomorphism and atypical mitosis, which were absent in current case. Although there is no biomarker that can differentiate between TAA and apocrine carcinoma, immunohistochemistry can be used as an adjunct in difficult cases. While both TAA and apocrine carcinoma show positivity for epithelial membrane antigen, gross cystic disease fluid protein 15, pan-cytokeratin and progesterone receptor, positivity for alpha-smooth muscle antigen and other myoepithelial markers is seen only in TAA.[5] In this case, immunohistochemistry for SMA was performed which was positive, thereby ruling out invasiveness [Figure 1f]. Recurrence or malignant behaviour has not been reported in isolated TAA after complete resection.[1] However, in this case, the patient will be kept on regular follow-up owing to the presence of worrisome microscopic features. Both clinicians and pathologists should be aware of such atypical presentations to arrive at the correct diagnosis by diligent microscopic evaluation and tailor appropriate treatment and follow-up protocol.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.
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