Infiltrates of Cells or Substances or Organisms

INFILTRATES OF CELLS, SUBSTANCES and ORGANISMS  IN THE DERMIS

Generally these conditions will give red non-scaly rashes as the "I" of EVIE is one of the letters used in the mnemonic for the red non-scaly disorders CUL DVA EVIE. (See You Later in the Department of Veterans Affairs EVIE) Infiltrates can be of cells, substances or organisms. The cells can be neutrophils, lymphocytes, histiocytes, Langerhans cells and  mast cells as well as substances such as uric acid, mucin, tattoo material, some introduced foreign materials such as paraffin or silica and filler substances used in cosmetic medicine. Organisms are typically deep fungi, Atypical Mycobacteria, M tuberculosis or M Leprae.

Look up more detailed histological descriptions of these conditions here.

Infiltrates of histiocytic cells are seen in xanthelasma and some of the other xanthomas in lepromatous leprosy and in Langerhans cell histiocytosis and also in the more common condition xanthogranuloma. 

Lymphocytic infiltrates are seen in lymphocytoma cutis and chronic lymphatic leukaemia while mainly plasma cell infiltrates can be seen in plasmacytoma associated with multiple myeloma. 

Mast cell infiltrates are seen in urticaria pigmentosa.

Neutrophilic infiltrates are a feature of granuloma faciale, erythema elevatum diutinum, Sweet's syndrome and cellulitis and rarely in a  granulocytic leukaemia. 

Eosinophilic infiltrates are seen in Well's syndrome and mixed infiltrates may be seen in some lymphomas.  Infections such as leishmaniasis will also give mixed infiltrates in the dermis.

Significant diffuse nodular infiltrates can be seen in lymphocytoma cutis, bite reactions and angiolymphoid hyperplasia with eosinophilia and some lymphomas.  It rarely also features in tertiary syphilis.

Most of the xanthomas will have lipid laden histiocytic cells throughout the dermis.  Sometimes these are known as foam cells.  Most of the lipid is actually lost during processing.  In lepromatous leprosy there may be sheets of foaming histiocytic cells but with an overlying grenz zone where the papillary dermis isn't involved.  There is also significant destruction and loss of the appendages which explains why these areas are often hairless and don't sweat.

The histiocytoses often affect the skin, some can be self-limiting but others such as Langerhans cell histiocytoses are more severe.  The dermis is full of large histiocytic cells with a round, oval notched or bean shaped nucleus.  There is sometime extravasation of erythrocytes which is reflected in the haemorrhage that may be associated with these lesions.  Tuton giant cells are a feature of xanthogranuloma along with the foamy histiocytic cells.

Lymphoma cutis will have a diffuse dermal infiltrate of lymphoid cells extending throughout the reticular dermis, sometimes into subcutaneous fat.  There is a degree of nuclear atypia and cells may infiltrate between the collagen fibres.  Leukaemia cutis has a similar picture but here you have got mainly immature leukocytes infiltrating.  In plasmacytomas the same picture but this time it is made up of atypical plasma cells that are in the dermis.  

In urticaria pigmentosa the infiltrate is of cuboidal mast cells, but they usually fill the papillary dermis and there is no grenz zone.

Granuloma faciale has mixed infiltrate and it may be seen as a nodular aggregate of lymphocytes and eosinophils.  Usually the infiltrates are confined to the upper dermis.  There may be associated leukocytoclastic vasculitis.

Sweet's syndrome gives a diffuse infiltrate of neutrophils.  The differential is a severe cellulitis, but in Sweet's there is often oedema of the papillary dermis and neutrophils are often both diffuse and perivascular with extensive nuclear fragments or dust but no true vasculitis hence no bruising.

Eosinophilic cellulitis or Well's syndrome has mainly an infiltrate of eosinophils.  Sometimes these degranulate and the collagen fibres are surrounded by this heavy staining eosinophilic material causing a flame figure.  The infiltrate may extend into the fat tissue or even muscle. 

In a cutaneous T-cell lymphoma there are atypical lymphocytes invading the overlying epidermis and showing epidermotropism forming Pautrier microabscesses.  In a B-cell lymphoma the infiltrate is mainly confined to the dermis and subcutaneous tissue but again there are atypical lymphocytic cells with abnormal nucleii.

Primarily nodular infiltrates in the dermis can be seen with lymphocytoma cutis.  Again there is often a grenz zone and the obvious lymphocytes and histiocytes may also be mixed with eosinophils.  The infiltrate is usually deep and there may be germinal centres with lymphoid follicles.  Lymphoid follicles can also be seen in marked insect bite reactions and also angiolymphoid hyperplasia with eosinophilia.

Arthropod bite reactions also give a significant infiltrate in the dermis but here you see a mixture of lymphocytes and eosinophils, sometimes with a few plasma cells.  As we have said already you may get lymphoid follicle with germinal centre formation and there is a bit of endothelial cell swelling as well.  The similarity with lymphocytoma cutis is reflected in the difficulty the pathologists have in making the diagnosis and also in an initial clinical diagnosis of lymphoma being made when it is just a severe insect bite reaction.  One of the classics clinically are the large nodules that occur with scabies as a post-scabetic phenomenon, particularly on the scrotum and genital area. 

Angiolymphoid hyperplasia with eosinophilia will also show lymphoid follicles in the dermis but there may be prominent vessels with plump endothelial cells protruding into the vascular lumen.  This is the hobnail appearance.  Epidermis is usually quite normal. 

The B-cell lymphomas typically give a very diffuse and nodular infiltrate of atypical lymphocytes in the dermis and there is marked nuclear pleomorphism when these cells are looked at with a higher power.  In lymphoma cutis you can have a very similar picture but in some cases the abnormal cells infiltrate in between the collagen fibres.

Sometimes metastatic disease, particularly from the breast will show infiltrates in the dermis but they are usually again single cell infiltrates in between the collagen fibres rather than any nodule formation.

Infiltrates of substances into the dermis can occur in Jesner's lymphocytic infiltrate and in scleredema where mucin is found between the collagen bundles.  Rarely introduced material such as paraffin or silicon can be injected into the skin.  Paraffin isn't used much nowadays but it used to give a very characteristic Swiss cheese appearance in the dermis where the lipid material was dissolved in the processing.

Erythropoetic protoporphyria can give pink material which is pretty amorphous and fills the upper half of the dermis.  A more subtle similar picture can be seen in amyloidosis where special stains are often necessary to show the pink amyloid proteins beneath the dermoepidermal junction.