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Cutaneous Signs as Predictors of Occult Malignancy: From Curth's
Postulates to a Probabilistic Framework for the First-Contact Clinician
ABSTRACT
Introduction. The skin is the only organ completely accessible to direct inspection, and therefore it often
becomes the first witness of an internal neoplasm that is still silent. However, the literature on
paraneoplastic dermatoses relies mostly on reports and case series, which has produced an extensive
body of knowledge in semiological description but poor in usable risk estimates. Objective. To critically
synthesize the evidence on skin signs associated with occult malignancy and to propose a probabilistic
interpretation framework, stratified by force of association, applicable in primary care and general
internal medicine. Methods. Narrative review with structured search in PubMed/MEDLINE, Scopus and
LILACS (January 1976 to August 2026), prioritizing population cohorts, case-control studies,
systematic reviews and guidelines. The signs were classified into three levels according to specificity,
magnitude of association and quality of evidence, and were examined under Curth's postulates as a
validation criterion. Results. A small group of dermatoses (acanthosis nigricans maligna, palms in the
gut, erythema gyratum repens, acquired hypertrichosis lanuginosa, necrolytic erythema migrans,
paraneoplastic pemphigus, Bazex's paraneoplastic acrokeratosis) shows an almost obligatory association
with neoplasia and warrants an immediate targeted search. A second group (adult dermatomyositis,
Sweet's syndrome, pyoderma gangrenosum, acquired ichthyosis, erythroderma, cutaneous vasculitis,
migratory thrombophlebitis) has a facultative association, the post-test probability of which depends on
age, clinical phenotype and serological markers. A third group (Leser-Trélat sign, chronic pruritus,
shingles) exhibits weak or controversial associations, with low absolute risks in population-based
cohorts. Skin metastases and genodermatoses with oncological predisposition are conceptually distinct
categories that must be differentiated from the paraneoplastic phenomenon. Conclusions. The predictive
value of a skin sign does not lie in its mere presence, but in the combination of intrinsic specificity,
clinical context, and pre-test probability. A stepwise approach—recognizing, stratifying, directing the
search—maximizes diagnostic yield and avoids both delay and overinvestigation, particularly in
resource-limited health systems.
Keywords: paraneoplastic syndromes, skin diseases, neoplasms, skin manifestations, early detection of
cancer
Artículo recibido 21 agosto 2026
Aceptado para publicación: 25 septiembre 2026