Dermatopathology

Reticulated acanthoma with sebaceous differentiation (RASD) is a rare, benign cutaneous neoplasm. Its variable clinical presentation frequently mimics both benign and malignant entities, posing a significant diagnostic challenge. We report a case of pigmented RASD in a 78-year-old Malay male of Fitzpatrick skin type IV who presented with a 5-year history of an 8 × 5 mm deeply pigmented, asymmetrical nodule on the left upper back, with a 2 mm central raised area showing less pigmentation. The lesion was clinically suspicious for malignant melanoma. Histopathological examination revealed characteristic features of RASD: a broad, plate-like, reticulated and pigmented epidermal proliferation with clusters of mature sebocytes at the bases of anastomosing rete ridges. Following biopsy confirmation, the residual lesion is being managed conservatively with observation. This case demonstrates an unusual heavily pigmented clinical presentation that completely obscured the typical yellowish hue associated with sebaceous differentiation, highlighting pigmented RASD as an important diagnostic pitfall in patients with skin of color. In conclusion, RASD should be included in the differential diagnosis of pigmented cutaneous lesions, especially in patients with skin of color. Recognition of this benign entity can prevent unnecessary aggressive surgical intervention.

Abductive reasoning, or abduction, is a key process in scientific discovery and medical diagnosis. In everyday dermatology and dermatopathology, however, it functions as the practical engine behind differential diagnosis, clinicopathologic correlation, and disciplined pattern recognition. In this paper, we retain the epistemological foundation of abduction but translate it into usable steps for clinicians and dermatopathologists. We distinguish abduction from deduction and induction; separate creative abduction (which generates new concepts) from selective abduction (daily diagnostic choice); and show how both operate within a simple Select-and-Test (ST) Model: select a hypothesis, deduce what else should be true, test against data, and then update. We then reinterpret Ackerman’s algorithmic method of pattern analysis as an operationalization of the ST-Model. Through a couple of concise case vignettes, we illustrate visual and manipulative abduction, nonmonotonic updates, and the role of artifacts (dermoscopy, DIF, stains) as so-called epistemic mediators. Finally, we map contemporary AI tools to selective abduction and propose practical guardrails for fairness, transparency, and accountability. The result is a pragmatic framework that preserves philosophical depth while addressing the daily needs of dermatologists and dermatopathologists in the clinic and at the microscope.

In this study we evaluated the expression of Angiopoietin 1, Angiopoietin 2, and Tie2 by immunohistochemistry in the skin of 10 patients with erythemato telangiectatic and papulopustular rosacea. Significantly increased expression of Tie2 and Angiopoietin 2 in the endothelial cells of the dermal vessels in rosacea skin vs. non-lesional skin (100% and 33.3% for Tie2, and 100% and 50% for Angiopoietin 2) was observed. There was no difference in the expression of Angiopoietin 1 and phosphorylated Tie2 (pTie2) between the lesional skin of rosacea and non-lesional skin.