Conference 09 - 2025 Case: 01 20251022

Wednesday Slide Conference, 2025-2026, Conference 9, Case 1

Signalment:

3 months-old, female, Piétrain x Large White, pig, Sus scrofa domesticus

History:

Gross Pathology: Multiple, 1-2 mm in diameter, non-raised, red to blue, irregular lesions were found diffusely distributed through the skin of the ventral and inguinal regionas well as the head, nose and ears. Upon incision, lesions were localized at the dermal/subcutaneous junction.

Laboratory Results:

Cells lining cystic cavities immunohistochemically stained positive with pan-cytokeratin and negative with CD31. Immunohistochemistry with Ki67 and alpha-SMA revealed a low proliferative index in the apocrine epithelial cells and strong positivity for alpha-SMA in the basal area of the cystic lesions.

Microscopic Description:

Haired skin (dorsal nose, three sections): Within the deep dermis and subcutis there are multiple well delineated clusters of variably distended apocrine glands with sinuous cystic cavities and partial tubular folding, which expand and replace dermal adipose tissue and muscle . Most of the clustered cysts are lined by a single layer of flattened columnar epithelial cells without apical blebbing. Adjacent smaller clusters of lesser distended glands exhibit one to several layers of more cuboidal epithelium. The outer layer of the cyst wall consists of thin layers of myoepithelial cells. Many gland lumina contain pale eosinophilic secretory product. Surrounding tissue and stroma comprises mild lymphoplasmacytic infiltrates.

Focally in the mid dermis and associated with a hair follicle there is a localized, well demarcated focus of moderate mixed cellular inflammation composed of macrophages, neutrophils and lesser lymphocytes and plasma cells. These encase numerous distorted and/or ruptured apocrine glands, infiltrate their epithelium and are present within the lumen of remaining glandular structures (foreign body type reaction). Macrophages frequently contain cellular debris.

The remaining epidermis and dermis are unremarkable.

Contributor's Morphologic Diagnoses:

Skin: cystic distention of apocrine glands, diffuse, severe, with compression of adjacent muscle tissue consistent with cutaneous apocrine cystomatosis.

Skin: hidradenitis and dermatitis, focally extensive, moderate, chronic, mixed cellular with apocrine gland rupture (foreign body type reaction).

Contributor's Comment:

TBD

Contributing Institution:

Ludwig-Maximilians-Universität München (LMU), Institute of Veterinary Pathology, Veterinärstr. 13, 80539 Munich, Germany www.patho.vetmed.uni-muenchen.de

in cooperation with:

Technical University of Munich (TUM), Institute of Pathology, Comparative Experimental Pathology (CEP), Trogerstr. 18, 81675 Munich, Germany web.med.tum.de/path/vergleichende-experimentelle-pathologie