In vivo identification of amyloid and mucin in basal cell carcinoma with combined reflectance confocal microscopy–optical coherence tomography device and direct histopathologic correlation
Authors: Aditi Sahu, Miguel Cordova, Melissa Gill, Christi Alessi-Fox, Cristián Navarrete-Dechent, Salvador González, Nicusor Iftimia, Milind Rajadhyaksha, Ashfaq A. Marghoob, Chih-Shan J. Chen
Journal: Journal of the American Academy of Dermatology (2019)

To the Editor: The combined reflectance confocal microscopy (RCM)-optical coherence tomography (OCT) device enables simultaneous, real-time visualization of cellular features in RCM and structural features in OCT, leading to better characterization of morphologic features and improved diagnosis and depth assessment of basal cell carcinoma (BCC).1Sahu A. Yélamos O. Iftimia N. et al.Evaluation of a combined reflectance confocal microscopy–optical coherence tomography device for detection and depth assessment of basal cell carcinoma.JAMA Dermatol. 2018; 154: 1175-1183Crossref PubMed Scopus (34) Google Scholar Amyloid and mucin deposits are established BCC histopathologic features. Primary cutaneous amyloidosis has been imaged with RCM,2Lei W. Ai-e X. Reflectance confocal microscopy for the characterization of primary cutaneous amyloidosis: a pilot study.Skin Res Technol. 2017; 23: 441-443Crossref PubMed Scopus (3) Google Scholar and BCC peritumoral-mucin on RCM has been histopathologically verified.3Ulrich M. Roewert-Huber J. González S. et al.Peritumoral clefting in basal cell carcinoma: correlation of in vivo reflectance confocal microscopy and routine histology.J Cutan Pathol. 2011; 38: 190-195Crossref PubMed Scopus (77) Google Scholar To our knowledge, however, no prior reports have demonstrated BCC-associated amyloid on RCM or OCT, and OCT descriptions of mucin have been inferential. Herein, we report in vivo characterization of amyloid and mucin through RCM-OCT, followed by precise histopathologic correlation. In the combined RCM-OCT device, en face or horizontal RCM images (field-of-view: 750 × 750 μm; lateral resolution: ∼1 μm; optical sectioning: ∼3 μm) are centered on vertical OCT images (field of view: 1000 × 2000 μm; lateral resolution: ∼5 μm; optical sectioning: ∼10 μm), which are postprocessed to obtain horizontal OCT. This study was performed under the Memorial Sloan Kettering Cancer Center IRB protocol 99-099. Consecutive BCCs were prospectively investigated for the presence of: (1) amyloid (amorphous, hyper-reflective, homogenous intratumoral/peritumoral globules) and (2) mucin (intratumoral/peritumoral hyporeflective areas). Next, RCM-OCT–guided punch biopsies (2-3 mm) were obtained, followed by horizontal (for RCM) or vertical (for OCT) sectioning to permit direct histopathologic correlation using hematoxylin and eosin (H&E), toluidine blue (TB, mucin), and Congo red (amyloid) staining. The size and distribution of hyper-reflective globules and hyporeflective areas in RCM, OCT, and histopathology were analyzed using the Fiji distribution of ImageJ software (National Institutes of Health, Bethesda, MD). Features of mucin and amyloid were identified in 6 patients (male/female ratio, 2:1; ages 24, 54, 65, 73, 78, 78 mean age, 61.5 years) with 8 BCCs (1 superficial; 6 nodular; 1 nodular-infiltrative). On histology, amyloid appeared as characteristic homogenous globules, bubble-gum pink on H&E, blue on TB, or red on Congo red. Mucin was an amorphous stringy substance, staining blue-purple-gray on H&E and magenta on TB. Hyper-reflective globules correlated with amyloid and hyporeflective areas correlated with mucin. Mucin deposition was intratumoral or peritumoral (Figs 1 and 2). Amyloid globules were distributed peritumorally (Fig 1) or within hyporeflective mucin pools (Figs 1 and 2).Fig 2Cases 2 and 3: Morphologic patterns of intratumoral amyloid deposits as well as intratumoral and peritumoral mucin deposits in nodular basal cell carcinomas confirmed on optical coherence tomography (OCT). Intratumoral deposits were present deep to the maximal imaging depth of reflectance confocal microscopy (RCM) and therefore only visualized by OCT. Case 2 shows a large intratumoral round-oval dark structure filled with hyper-reflective globules on (A) vertical and (B) horizontal OCT corresponding to a round collection of mucin (red asterisks) intermixed with amyloid globules (yellow arrows) within the center of the tumor nodule. Amyloid appeared characteristic bubble gum pink on (C) hematoxylin and eosin (H&E) and (D) blue on toluidine blue (TB). Peritumoral mucin (red arrows) is identified as a dark peritumoral rim on (A, B) OCT and corresponds to stringy amorphous material which is (C) purple-gray on H&E and (D) magenta on TB. Case 3 harbors a large tumor nodule with a central pool of mucin (red asterisk), which is (E, F) dark on OCT and amorphous, stringy, purple-gray material on (G) H&E and (H) Congo red (CR). Hyper-reflective aggregated globules (yellow arrows) noted within the mucin pool on (E, F) OCT are partially obscured by mucin on TB but (H) confirmed to be amyloid (yellow arrows) on CR-stained histopathology. Also noted is a characteristic peritumoral rim of mucin (red arrows), which appears dark on (E) OCT and white due to mucin washout on (G) H&E histopathology.View Large Image Figure ViewerDownload Hi-res image Download (PPT) In 6 of 8 cases, we identified mucin and amyloid on RCM and OCT. In 2 cases, the features were only present in the deep dermis and therefore visualized only on OCT (8 of 8). The amyloid globule/cluster size ranged between 9 to 32 μm on horizontal RCM, 11 to 23 μm on horizontal histology (TB/Congo red), 26 to 85 μm on vertical OCT, and 15 to 95 μm on vertical histology. The large mucin pool (Fig 1) measured 170 × 220 μm (RCM), 180 × 275 μm (OCT), and 170 × 270 μm (histology). Amyloid and intratumoral mucin deposition are frequently observed in less aggressive nodular BCCs (up to 85% positive for amyloid).4Cohen P.R. Basal cell carcinoma associated with secondary localized cutaneous amyloid deposits: case report and review.Cureus. 2019; 11: e3879PubMed Google Scholar Thus, noninvasive visualization of prominent amyloid and mucin features may be clinically relevant for the diagnosis of less aggressive BCCs, which in turn can help streamline management. Furthermore, given the anticipated increased use of RCM-OCT Current Procedural Terminology (American Medical Association, Chicago, IL) codes,5Current Procedural Terminology, Professional Edition. American Medical Association, Chicago IL2016Google Scholar these features should be identified by physicians performing RCM, OCT, or both.