TABLE 2.
SQUAMOUS CELL CARCINOMA: RCM TERMS, FREQUENCY OF LITERATURE USE, SUGGESTED GROUPING BASED ON SIMILARITY IN DEFINITIONS AND HISTOPTAHOLOGICAL CORRELATES
| RCM Term | Frequency of use of individual RCM terms | Definition | Histopathological correlates |
|---|---|---|---|
| SUPRABASAL EPIDERMIS TERMS (N=37; 63.7%) | |||
| Hyperkeratosis32,35,37 | 3 | Thickening of the stratum corneum >15um | Hyperkeratosis |
| Subtotal (weight***) | 3 (3.2%) | ||
| Parakeratosis32,34–37 | 5 | Nucleated cells appearing as dark nuclei surrounded by a bright outline centrally stratum corneum corneocytes | Parakeratosis |
| Subtotal (weight***) | 5 (5.3%) | ||
| Detached corneocytes32 | 1 | White, highly refractive polygonal structure of approximately 30–40 um in diameter in the stratum corneum | Detached corneocytes |
| Polygonal nucleated cells at the stratum corneum9 | 1 | ||
| Disruption/individual cells36 | 1 | ||
| Individual corneocytes37 | 1 | ||
| Superficial epidermal disruption33 | 1 | ||
| Subtotal (weight***) | 5 (5.3%) | ||
| Stratum corneum disruption | 1 | Alteration of the smooth contour of the stratum corneum observed in mosaic images | N/A |
| Subtotal (weight***) | 1 (1.1%) | ||
| Orthokeratosis32 | 1 | Hyperkeratosis without parakeratosis | Orthokeratosis |
| Subtotal (weight***) | 1 (1.1%) | ||
| Scale9,34,36 | 3 | Variably refractile, amorphous material in stratum corneum | Hyperkeratosis |
| Subtotal (weight***) | 3 (3.2%) | ||
| Atypical honeycomb pattern6,9,31–33,35,36* | 7 | Irregularly shaped cells deviating from the normal honeycomb pattern | Variation in cellular and nuclear shape and size of epidermal keratinocytes |
| Diamond shaped honeycomb6 | 1 | ||
| Irregular honeycomb pattern29,34 | 2 | ||
| Subtotal (weight***) | 10 (10.7%) | ||
| Architectural disarray28,32 | 2 | Severe disarranged epidermal pattern in which the honeycomb pattern is no longer visible | Severe variation in cellular and nuclear shape and size of epidermal keratinocytes |
| Honeycomb atypical and disarrayed6 | 1 | ||
| Loss of regular stratification of epidermal layers29 | 1 | ||
| Disarranged epidermal pattern9,31,36 | 3 | ||
| Architectural disarrangement35,37 | 2 | ||
| Subtotal (weight***) | 9 (9.6%) | ||
| Cellular and nuclear pleomorphism (of the epidermis)32 | 1 | Variation in cellular and nuclear shape and size | Variation in cellular and nuclear shape and size |
| Different size and shape of the nuclei of keratinocytes29 | 1 | ||
| Keratinocyte pleomorphism37 | 1 | ||
| Pleomorphic nuclei of keratinocytes28 | 1 | ||
| Subtotal (weight***) | 4 (4.3%) | ||
| Irregular borders of keratinocytes29 | 1 | Irregular borders of keratinocytes | N/A |
| Subtotal (weight***) | 1 (1.1%) | ||
| Irregular intercellular keratinocyte connections29 | 1 | Irregular intercellular keratinocyte connections | N/A |
| Subtotal (weight***) | 1 (1.1%) | ||
| Targetoid cells32,33,35,36† | 4 | Two cell types have been described: Large cell with a bright center and a dark peripheral halo (denoted as ′Targetoid cells 1′);32,33 Large cell with a dark center and a bright rim surrounded by a dark halo (denoted as ′Targetoid cells 2′)32,33 |
Dyskeratotic keratinocytes within the epidermis |
| Dyskeratotic areas29 | 1 | ||
| Round nucleated cells at spinous-granular layer9 | 1 | ||
| Dyskeratotic cell28 | 1 | ||
| Subtotal (weight***) | 7 (7.5%) | ||
| Multinucleated keratinocytes32 | 1 | Large cells with tight aggregates of bright nuclei | Multinucleated keratinocytes |
| Large cells with aggregated nuclei in the epidermis33 | 1 | ||
| Subtotal (weight***) | 2 (2.1%) | ||
| Spongiosis32,35 | 2 | Enlargement of the bright intercellular spaces due to fluid accumulation between keratinocytes | Spongiosis |
| Subtotal (weight***) | 2 (2.1%) | ||
| Exocytosis32 | 1 | Inflammatory cells appearing as highly refractive structures in the epidermis | Exocytosis |
| Subtotal (weight***) | 1 (1.1%) | ||
| Spindle-shaped cells with dendritic branches infiltrating the epidermis34 | 1 | Bright cells with elongated branching structures extending from fusiform cell body; seen at the spinous and granular layers of the epidermis (corresponding to Langerhans cells of pigmented SCC or pigmented AK) | Langerhans cells infiltrating the epidermis |
| Dendritic cells in the epidermis35,36¶ | 2 | ||
| Subtotal (weight***) | 2 (2.1%) | ||
| Erosion/ulceration35 | 1 | Dark areas, with sharp borders and irregular contours, filled with amorphous material, cellular debris and small particles | Ulceration of the epidermis |
| Subtotal (weight***) | 1 (1.1%) | ||
| Corneal pseudocysts36 | 1 | Well circumscribed large, round, highly refractile intraepidermal structures | Intraepidermal cysts |
| Subtotal (weight***) | 1 (1.1%) | ||
| Speckled nucleated cells in the epidermis | 1 | Roundish-to-polygonal cells with speckled appearance and dark nucleus in the epidermis. Size is slightly larger than surrounding keratinocytes. They are larger than lymphocytes and have polygonal shape that differentiate them from dendritic cells | N/A |
| Subtotal (weight***) | 1 (1.1%) | ||
| Total for Suprabasal Epidermis (weight) | 60 (64.5%) | ||
| BASAL LAYER/DEJ/SUPERFICIAL DERMIS TERMS (N=21; 36.2%) | |||
| Elongated dermal papillae28 | 1 | Elongated dermal papillae | N/A |
| Subtotal (weight***) | 1 (1.1%) | ||
| Edged papillae34 | 1 | Multiple scattered dermal papillae demarcated by a rim of bright cells. In pigmented SCC, the edged papillae are mostly peripheral in location with widened interpapillary spaces | Atypical pigmented keratinocytes |
| Subtotal (weight***) | 1 (1.1%) | ||
| Mottled pigmentation36¶ | 1 | Corresponds to presence of clustered bright keratinocytes detectable in context of honeycombed pattern | Basilar pigmented keratinocytes |
| Subtotal (weight***) | 1 (1.1%) | ||
| Keratin pearl32,35 | 2 | Whorl-shaped accumulation of keratin appearing as highly refractive, speckled structure in the dermis†† | Keratinization |
| Subtotal (weight***) | 2 (2.1%) | ||
| Convoluted glomerular vessel6 | 1 | Coiled canalicular vessels | Aberrant vessels |
| Subtotal (weight***) | 1 (1.1%) | ||
| Linear vessels36 | 1 | Vessels oriented parallel to the imaging plane | Aberrant vessels |
| Subtotal (weight***) | 1 (1.1%) | ||
| Round blood vessels traversing the dermal papilla9,36 | 2 | Dilated blood vessels within the dermal papillae that run perpendicular to the horizontal RCM plane of imaging / Dilated blood vessels within the dermal papillae looping perpendicular to the horizontal plane of RCM imaging. The presence of multiple looping vessels renders the dermal papillae a Button-hole like appearance | Aberrant and neo formed vessels |
| Round-to-oval vessels33 | 1 | ||
| Buttonhole vessels35,36 | 2 | ||
| Dilated looping blood vessels withinpapillae34,35 | 2 | ||
| Subtotal (weight***) | 7 (7.5%) | ||
| Increased number of blood vessels32,37 | 2 | > 5 blood vessels per 0.5 × 0.5 mm | Neovascularization |
| Subtotal (weight***) | 2 (%) | ||
| Increased blood vessel dilatation32,37 | 2 | Blood vessels of diameter >5 um | Aberrant vessels |
| Subtotal (weight***) | 2 (2.1%) | ||
| S-shaped vessels33 | 1 | Round-to-oval vessels with increased tortuosity at the center of the dermal papillae, S-shaped at lower papillary dermis | N/A |
| Subtotal (weight***) | 1 (1.1%) | ||
| Solar elastosis32,37 | 2 | Network of thick, highly refractile collagen bundles intermixed with moderately refractive, lace-like elastic fibers | Solar elastosis |
| Curled fibers36 | 1 | ||
| Subtotal (weight***) | 3 (3.2%) | ||
| Huddled collagen bundles36 | 1 | Large hyporefractive blotches of amorphous and hyporeflective material; individual collagen fibers are no longer visible | N/A |
| Subtotal (weight***) | 1 (1.1%) | ||
| Coarse collagen bundles36 | 1 | Bright fibrillar structures that appear finely reticulated, forming a web-like | N/A |
| Subtotal (weight***) | 1 (1.1%) | ||
| Nest-like structures32,35 | 2 | Round, demarcated structures in the dermis that are often surrounded by fibrosis | N/A |
| Subtotal (weight***) | 2 (2.1%) | ||
| Plump cells34–36 | 3 | Melanophages | Melanin-laden macrophages in dermis |
| Subtotal (weight***) | 3 (3.2%) | ||
| Speckled nucleated cells in the dermis35 | 1 | Roundish to polygonal cells with speckled appearance and dark nucleus within the dermis. They are larger than the usual size of lymphocytes and have a polygonal shape that differentiate them from plump bright cells | N/A |
| Subtotal (weight***) | 1 (1.1%) | ||
| Inflammatory cells32,33,37 | 3 | Highly refractile structures of 8–10 um in diameter located in the epidermis or dermis | Inflammatory cells: lymphocytes and neutrophils |
| Subtotal (weight***) | 3 (3.2%) | ||
| Total for basal layer/DEJ/superficial dermis | 33 (35.4%) | ||
| TOTAL TERMS FOR SCC (N=58) | 93 (100%) | ||
*
Most studies recommend stating partial thickness or full thickness atypia to differentiate between actinic keratosis and squamous cell carcinoma.
**
Superscripted numbers denote reference numbers.
***
Weight calculates the relative frequency of use for each subgroup of terms; the denominator is the total times SCC terms were used in the literature (n=71).
†
This term has been mainly described in association with Bowen’s disease.
¶
Features of pigmented actinic keratosis
††
This feature can be also seen at the level of the epidermis.