Page 401 - Textbook of Pathology, 6th Edition

diagnosed in asymptomatic healthy aging population—1% 385
at 50 years of age and in 10% individuals older than 75 years.
This makes it the most common form of plasma cell dyscrasia.
The defining criteria for MGUS are as under:
i) M-protein in serum <3 gm/dl
ii) Marrow plasmacytosis <10%
iii) No evidence of other B-cell proliferative disorder
iv) Absence of myeloma-related end-organ tissue damage
(i.e. absence of lytic bone lesions, high calcium level,
anaemia).
The condition needs to be cautiously distinguished from
myeloma and long term follow-up is required. In fact, MGUS
has been considered as a forerunner of multiple myeloma in
many studies because MGUS has been found to have the
same chromosomal abnormalities as in myeloma.
Figure 14.28 Metastatic carcinomatous deposits in the matted mass
LYMPH NODE METASTATIC TUMOURS of lymph nodes. There are areas of necrosis in the circumscribed nodular CHAPTER 14
areas.
The regional lymph nodes draining the site of a primary
malignant tumour are commonly enlarged. This enlargement i) Demonstration of common antigens on these cells by
may be due to benign reactive hyperplasia or metastatic tumour immunohistochemical stains for S-100 protein, CD1a and HLA-
deposits. DR.
1. Benign reactive hyperplasia, as already discussed (page ii) Electron microscopic demonstration of histiocytosis-X bodies
343), is due to immunologic reaction by the lymph node in or Birbeck granules in the cytoplasm. These are rod-shaped
response to tumour-associated antigens. It may be expressed structures having dilated tennis-racket like terminal end.
as sinus histiocytosis, follicular hyperplasia, plasmacytosis Their function is not known but they arise from receptor-
and occasionally may show non-caseating granulomas. mediated endocytosis of langerin found in human epidermal
cells, a protein involved in Birbeck granule biosynthesis.
2. Metastatic deposits in regional lymph nodes occur most The three disorders included in the group are briefly
commonly from carcinomas and malignant melanoma. considered below.
Sarcomas often disseminate via haematogenous route but
uncommonly may metastasise to the regional lymph nodes. Eosinophilic Granuloma
Metastatic tumour cells from the primary malignant tumour
are drained via lymphatics into the subcapsular sinuses Unifocal eosinophilic granuloma is more common (60%) than
initially but subsequently the lymph node stroma is also the multifocal variety which is often a component of Hand- Disorders of Leucocytes and Lymphoreticular Tissues
invaded. The pushing margins of advancing metastatic Schüller-Christian disease (described below). Most of the
tumour in stroma of lymph node is characteristically well patients are children and young adults, predominantly males.
demarcated. Areas of necrosis are frequent in metastatic carci- The condition commonly presents as a solitary osteolytic
nomas (Fig. 14.28). lesion in the femur, skull, vertebrae, ribs and pelvis. The
The morphologic features of primary malignant tumour diagnosis requires biopsy of the lytic bone lesion.
are recapitulated in metastatic tumour in lymph nodes.
Microscopically, the lesion consists largely of closely-
packed aggregates of macrophages admixed with variable
HISTIOCYTIC NEOPLASMS:
number of eosinophils (Fig. 14.29). The macrophages
LANGERHANS’ CELL HISTIOCYTOSIS contain droplets of fat or a few granules of brown pigment
indicative of phagocytic activity. A few multinucleate
Langerhans’ cell histiocytosis (LCH) is a group of rare macrophages may also be seen. The cytoplasm of these
malignant proliferations of dendritic cells or macrophages macrophages may contain rod-shaped inclusions called
and includes three clinicopathologically related conditions histiocytosis-X bodies or Birbeck granules, best seen by
ocurring in children: eosinophilic granuloma, Hand-Schüller- electron microscopy.
Christian disease and Letterer-Siwe syndrome. Earlier, this
group was referred to as histiocytosis-X but now following Clinically, unifocal eosinophilic granuloma is a benign
facts about this group are known: disorder. The bony lesion remains asymptomatic until the
Firstly, histiocytosis-X are not proliferations of unknown erosion of the bone causes pain or fracture. Spontaneous
origin (X-for unknown) but proliferating cells are actually fibrosis or healing may occur in some cases, while others
Langerhans’ cells of marrow origin. Langerhans’ cells are may require curettage or radiotherapy.
normally present mainly in the epidermis of the skin but also
in some other organs. Hand-Schüller-Christian Disease
Secondly, the three conditions included under histio- A triad of features consisting of multifocal bony defects, diabetes
cytosis-X are actually different expression of the same basic insipidus and exophthalmos is termed Hand-Schüller-Christian
disorder. This concept has emerged from 2 features: disease. The disease develops in children under 5 years of