Diagnostic concordance and delayed recognition: a case of atypical Kaposi sarcoma

Accurate diagnosis depends on concordance among clinical findings, histopathologic features, and patient context; when these elements diverge, even well-characterized diseases may evade timely recognition.

We report a case of Kaposi sarcoma (KS) in a 47-year-old woman who presented with a chronic, unilateral, non-violaceous eruption of the left lower extremity. Serial clinical evaluations and biopsies demonstrated dermal fibrosis, vascular congestion, and hemosiderin deposition without the classic histopathologic features typically associated with KS, leading to repeated interpretation as reactive or stasis-related disease. Despite progressive clinical findings, apparent concordance between benign-appearing clinical and histologic features delayed diagnostic reassessment. Ultimately, expert dermatopathology consultation with immunohistochemical staining confirmed KS in the setting of previously unrecognized HIV infection.

This case illustrates how atypical disease biology, false reassurance from partial concordance, fragmented care, and social determinants of health can disrupt diagnostic synthesis and obscure evolving malignancy. When disease behavior contradicts initial interpretations, deliberate reassessment and longitudinal integration of data across encounters and specialties are essential to avoid delayed diagnosis, particularly in patients facing barriers to longitudinal continuity of care.