Diascopy

Diascopy is a test for blanchability performed by applying pressure with a finger or glass slide and observing color changes.^[2][3][4][5]

Diascopy of a red dot basal cell carcinoma on the left mid back of a 74-year-old female. The red dot basal cell carcinoma on the left mid back is circled; the tumor blanches when a glass microscope slide is pressed against it. From a case series by Philip R Cohen, 2017.^[1]

It is used to determine whether a lesion is vascular (inflammatory or congenital), nonvascular (nevus), or hemorrhagic (petechia or purpura). Hemorrhagic lesions and nonvascular lesions do not blanch ("negative diascopy"); inflammatory lesions do ("positive diascopy"). Diascopy is sometimes used to identify sarcoid skin lesions, which, when tested, turn an apple jelly color.

References

1. Cohen PR (March 2017). "Red Dot Basal Cell Carcinoma: Report of Cases and Review of This Unique Presentation of Basal Cell Carcinoma". Cureus. 9 (3): e1110. doi:10.7759/cureus.1110. PMC 5408973. PMID 28465868.
2. Marks, James G; Miller, Jeffery (2006). Lookingbill and Marks' Principles of Dermatology (4th ed.). Elsevier Inc. Page 29. ISBN 1-4160-3185-5.
3. Goldman, L.; Plotnick, H.; Balinkin, I. (May 9, 1957). "Investigative and clinical studies with diascopy in dermatology". Archives of Dermatology. 75 (5): 699–705. doi:10.1001/archderm.1957.01550170067012. PMID 13410135 – via PubMed.
4. D, Pérez-López; M, Peña-Cristóbal; EM, Otero-Rey; I, Tomás; A, Blanco-Carrión (October 1, 2016). "Clinical value of diascopy and other non-invasive techniques on differential diagnosis algorithms of oral pigmentations: A systematic review". Journal of Clinical and Experimental Dentistry. 8 (4): e448–e458. doi:10.4317/jced.53005. PMC 5045694. PMID 27703615.
5. Rudd, M.; Eversole, R.; Carpenter, W. (March 9, 2001). "Diascopy: a clinical technique for the diagnosis of vascular lesions". General Dentistry. 49 (2): 206–209. PMID 12004702 – via PubMed.