Pitted keratolysis is a superficial bacterial infection of the stratum corneum on weight-bearing areas of the soles (and less commonly palms) characterized by malodor and discrete crateriform pits. It is caused by gram-positive bacteria (Corynebacterium, Kytococcus, Dermatophilus) that produce keratin-degrading…

Erythrasma is a superficial bacterial infection of the stratum corneum caused by Corynebacterium minutissimum. It presents as well-demarcated, brownish-red patches in intertriginous areas with fine scale and minimal symptoms. Wood’s lamp reveals coral-red fluorescence due to coproporphyrin III, aiding diagnosis.…

Epidermal inclusion cysts are common benign intradermal cysts lined by stratified squamous epithelium and filled with keratin. They present as slow-growing, firm, dome-shaped nodules with a central punctum, most often on the face, neck, upper back, and trunk. They may…

Lipomas are common benign tumors composed of mature adipocytes, usually presenting as soft, mobile, painless subcutaneous nodules on the trunk, shoulders, neck, or extremities. Most are solitary and small (<5 cm), but multiple lesions can occur, including in familial multiple…

Sézary syndrome is an aggressive leukemic variant of CTCL characterized by erythroderma, generalized lymphadenopathy, and malignant T‑cell (Sézary cell) circulation. It carries a poorer prognosis than classic MF and requires systemic therapy, often multimodal, with a focus on controlling pruritus,…

Mycosis fungoides is the most common primary cutaneous T‑cell lymphoma (CTCL), typically an indolent CD4+ epidermotropic malignancy presenting with patches and plaques on sun-protected sites. Disease course is heterogeneous; early stages are skin-limited with excellent survival, while tumor, erythrodermic, or…

Dermatofibromas are common benign dermal proliferations, often presenting as firm papules or nodules on the extremities of young to middle-aged adults. They are usually asymptomatic but may be pruritic or tender. The characteristic clinical sign is a central “dimple” on…

Seborrheic keratoses are common, benign epidermal tumors that present as well-demarcated, “stuck-on,” waxy papules or plaques with variable pigmentation. They arise in adulthood and increase with age. While asymptomatic, SKs can itch, become irritated, or cosmetically concerning. The primary clinical…

Merkel cell carcinoma is a rare, aggressive neuroendocrine skin cancer with high propensity for local recurrence and early metastasis. It is associated with Merkel cell polyomavirus (MCPyV) integration in ~60–80% of cases and/or UV-induced mutations. Clinically, it presents as a…

Cutaneous melanoma is a malignant tumor of melanocytes with high metastatic potential. Incidence has risen globally, though mortality has improved with earlier detection and effective systemic therapies. Subtypes include superficial spreading, nodular, lentigo maligna (melanoma in situ on chronically sun-damaged…